Endocrine complications after radiotherapy for tumors of the head and neck were thought to be relatively rare. During radiotherapy of nasopharyngeal cancer, neoplasms of the paranasal sinuses, optic nerves and intracranial tumors other than the pituitary, the hypothalamic-pituitary axis is included in the field of irradiation, as is the thyroid gland when the cervical nodes contain metastatic disease or the neck is irradiated prophylactically. Our retrospective investigations have shown that hypopituitarism secondary to hypothalamic lesion or primary pituitary damage may be more common than suspected in the past and primary hypothyroidism may result from irradiation of the regional neck nodes. Prospective study of a similar group of patients has been initiated and we accrued a large number of patients. In the coming three years requested, we will have significant follow up on these patients and data to be of statistical significance. We will determine the interval between radiotherapy and development of endocrine complication so that treatment can be initiated early. The dose, technique, and period of radiotherapy will be correlated with the endocrine results to delineate the lowest threshold for damage by irradiation. It will also be determined if children are more susceptible to damage by irradiation. The information may enable us to minimize the endocrine complication without compromising treatment. To determine the function and detect any neoplastic changes which may occur in the thyroid and parathyroid glands as a result of radiotherapy not only in the patients with head and neck tumors, but also in patients with Hodgkin's disease involving the neck glands before and after radiotherapy and compare these patients with a similar group of Hodgkin's patients who received no neck irradiation. The effectiveness of prophylactic thyroid suppression by thyroid hormone during the irradiation of the neck on subsequent functional abnormalities of the thyroid gland will be determined.